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Membranes > Dunns EXTRA stuff > Flashcards

Dunns EXTRA stuff Flashcards

supplementary carbohydrate metabolism

1
Q

What are glycosaminoglycans?

A

GAGS

  • long unbranched polysaccharides
  • repeating disaccharide unit of hexosamine or hexose sugar and uronic acid or hexose sugar
  • e.g. Heparin
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2
Q

What can the hexosamines or the hexose sugar be in the GAG?

A

Hexosamine:
N-acetylglucosamine or N-acetylgalactosamine
Hexose Sugar:
Galactose

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3
Q

What can the uronic acid or the hexose sugar be in the GAG?

A

Uronic Acid:
Glucuronic acid or iduronic acid
Hexose Sugar:
Galactose

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4
Q

When are the disaccharides in GAGS sulfated?

A

Most cases

- exception is hyaluronic acid

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5
Q

What are glycosamioglycans disorders?

A
  • lysosomal storage disorders
  • inherited diseases called MPS diseases
  • defects in lysosomal enzymes associated with metabolism/ breakdowns of GAGs leading to an accumulation of GAGs in cells
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6
Q

Name and describe a MPS disease.

A 
Sanfilippo disease
- rare
- primarily effects heparan sulfate
- causes mental deterioration
Effects cornea, heart, lungs, brain and mental functions
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7
Q

Where are GAGs prevalent?

A

In proteoglycans

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8
Q

What is the structure of proteoglycans?

A
  • protein with one of multiple (>100) GAGs covalently attached
  • up to 95% of proteoglycan
  • trisaccharide links GAGs to the protein
  • large molecules
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9
Q

What are trisaccharides in GAGs composed of?

A

2 galactose residues and a xylose residue

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10
Q

What are the properties of GAGs?

A
  • highly negatively charged

- highly hydrophilic

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11
Q

What can GAGs do in the body?

A
  • concentrate cations such as sodium
  • can form porous hydrated gels that are active in the extracellular matrix providing mechanical support, infused with chains
  • can form long chains (withstand compression forces and act as lubricants around joints)
  • chains are inflexible
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12
Q

What are glycoproteins?

A
  • oligosaccharide chains covalently linked to proteins
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13
Q

Name an example of a glycoprotein.

A

Erythropoietin (EPO) is a glycoprotein hormone

- controls rbc production (haemopoiesis)

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14
Q

What are glycoproteins usually composed of?

A

No GAGs
Usually, glucose, galactose manose etc
- not typically sulfated

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15
Q

How does the ratio of glycoproteins compare to that or proteoglycans?

A

Protein:sugar ratio is higher, more proteins than hexose sugars in glycoproteins than in proteoglycans

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16
Q

How do we acquire fatty acids?

A

Through diet

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17
Q

Where can we synthesise fatty acids?

A

Liver and adipose fat

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18
Q

What are the 4 fatty acid synthesis steps?

A
  1. condensation of acetyl-ACP and malonyl ACP
  2. reduction
  3. dehydration
  4. reduction to form butyryl-ACP
    - further processes add malonyl-acp to synthesise a c16 or c18 fatty acid
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19
Q

What is ACP?

A

An acyl carrier protein

20
Q

Draw the diagram of fatty acid synthesis (including enzymes)

A

-

21
Q

Which is the rate-limiting step in fatty acid synthesis?

A

Synthesis of malonyl-CoA

22
Q

How do you synthesise malonyl-CoA?

A

Acetyle-CoA + AYP + HCO3- -> Malonyl-CoA + ADP + Pi + H+

using enzyme acetyl-CoA carboxylase

23
Q

How do you control fatty acid metabolism?

A

Regulation of acetyl-CoA carboxylase

24
Q

What happens during the inactive phase of acetyl-CoA carboxylase?

A
  • post translational phosphorylation
  • during fasting state, presence of glucagon and adrenaline (along with protein kinases) will phosphorylate the carboxylase
25
Q

What happens during the active phase of acetyl-CoA carboxylase?

A
  • inactive phosphate has been dephosphorylated

- during fed state, insulin (along with protein kinase) will dephosphorylate the carboxylase

26
Q

What is the word for an inactive and active protein complex?

A

inactive - monomeric

active - polymeric

27
Q

When can the partially active state for carboxylase occur?

A
  • build of citrate from the TCA cycle
  • acetyl-coA is no longer needed in TCA and so can be used in synthesis of fatty acids
  • carboxylase is phosphorylated but also has a non covalently bound citrate complex
  • partial activation
28
Q

What is fatty acid elongation?

A

synthesis of longer than C16/C18 fatty acids, derived form diet and synthesis

29
Q

What is the difference between fatty acid elongation and fatty acid synthesis?

A
  • occurs in the ER

- applies CoA not ACP conjugates

30
Q

What are the similarities between fatty acid elongation and fatty acid synthesis?

A
  • applies reductase, hydratase enzymes
  • applies malonyl CoA as a 2 C donor
  • requires NADPH as a reducing agent
  • can operate for saturated and unsaturated fatty acids
31
Q

What is fatty acid desaturation- aerobic desaturation?

A
  • provides mono or polyunsaturated fatty acids from either saturated or unsaturated fatty acids
32
Q

What are the 3 desaturase enzymes in mammals? Where do they create double bonds

A

delta 5,6 and 9

- create double bonds at C position 5, 6 and 9

33
Q

Which enzymes are involved in fatty acid desaturation?

A

NADH-cytochrome b5 reductase, cytochrome b5 and desaturase

34
Q

What are the two essential fatty acids for humans?

A

Linolenic acid and alpha-linolenic acid

35
Q

What are Linolenic acid and alpha-linolenic acid used for?

A
  • to generate new fatty acids that have double bonds beyond the C9 position
36
Q

What are essential fatty acids?

A

Fatty acids required to be delivered through the diet as cannot be synthesised

37
Q

What is arachidonic acid?

A

A precursor for major prostaglandins, inc thromboxane A2 (through thromboxane synthases)

38
Q

Where can arachidonic acid and other major inflammatory and pain mediators be found in the body? Inc examples.

A

local hormones produced and applied at site of action
thromboxane A2, generated in blood platelets for vasoconstrictions
Prostaglandin E2, generated in the uterus and generates muscle contractions during brith

39
Q

What are the COX enzymes used for?

A
  • enzymes involved in the synthesis of PGH2 (prostaglandins H2) from Arachidonic acid
40
Q

Where are COX 1 & COX 2 enzymes found?

A

COX 1 is widely expressed in many tissues
COX 2 is not observed in healthy tissues
- inflammatory mediator response

41
Q

What do anti-inflammatory drugs inhibit?

A

Aspirin & ibuprofen are non specific and inhibit both

  • inhibition of COX1 lead to bleeding and gastric inflammation
  • inhibition of COX2 target inflammatory action (more specific effects)
42
Q

What are steroids?

A
  • class of lipids with 4 fused cycloalkane rings and a C17 backbone
  • 3 cyclohexane and 1 cyclopentane ring
43
Q

What are examples of steroids?

A
  • cholesterol
  • bile acid
  • progesterone
44
Q

What is cholesterol?

A
  • steroid

- essential metabolite in mammalian systems and a precursor to other important metabolites

45
Q

Where is cholesterol synthesises?

A

cytoplasm mainly in the liver, but also: intestine, adrenal glands and reproductive organs

46
Q

What are the 3 main steps of cholesterol biosynthesis

A

step 1: acetyl-CoA to mevalonate
step 2: mevalonate to squalene
step 3: squalene to cholesterol (via lanosterol)

47
Q

How many moles of acetyl-CoA, ATP and NADPH is used up in the synthesis of cholesterol?

A

18 moles of acetyl-CoA, 36 moles of ATP and 16 moles of NADPH

Membranes (19 decks)

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